Karyopherin beta 2 mediates nuclear import of a mRNA binding protein
Karyopherin beta 2 mediates nuclear import of a mRNA binding protein
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DOI：
10.1073/pnas.94.10.5055
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发表时间：
1997-05-13
影响因子：
11.1
通讯作者：
Blobel, G
中科院分区：
文献类型：
--
作者：
Bonifaci, N;Moroianu, J;Blobel, G
我们已经克隆并测序了人核粘蛋白β2，也称为转运蛋白。在溶液结合实验中，重组β2直接与重组核转录因子结合蛋白A1结合。结合被代表A1‘S先前特征的M9核定位序列的肽所抑制，但不被代表经典核定位序列的肽所抑制。在溶液结合实验中，核粘附素β1和核粘附素β2都竞争结合固定化重复核孔蛋白Nup98。在洋地黄素渗透的细胞中，β2能够将铝停靠在核缘，并将其传递到核质中。在低浓度的β2作用下，外源性的GTP酶Ran不能刺激进口，而在高浓度的β2作用下，RAN对进口有明显的刺激作用。与溶液结合结果一致，核粘附素β2抑制核粘附素α/β1介导的含有底物的经典NLS的导入，反之亦然，核粘附素β1抑制β2介导的A1底物的导入，表明这两条导入途径在β1和β2对接水平上合并，重复核孔蛋白。
We have cloned and sequenced cDNA for human karyopherin beta 2, also known as transportin. In a solution binding assay, recombinant beta 2 bound directly to recombinant nuclear mRNA-binding protein A1. Binding was inhibited by a peptide representing A1's previously characterized M9 nuclear localization sequence (NLS), but not by a peptide representing a classical NLS. As previously shown for karyopherin beta 1, karyopherin beta 2 bound to several nucleoporins containing characteristic peptide repeat motifs, In a solution binding assay, both beta 1 and beta 2 competed with each other for binding to immobilized repeat nucleoporin Nup98. In digitonin-permeabilized cells, beta 2 was able to dock Al at the nuclear rim and to impart it into the nucleoplasm. At low concentrations of beta 2, there was no stimulation of import by the exogenous addition of the GTPase Ran, However, at higher concentrations of beta 2 there was marked stimulation of import by Ran. Import was inhibited by the nonhydrolyzable GTP analog guanylyl imidodiphosphate by a Ran mutant that is unable to hydrolyze GTP and also by wheat germ agglutinin, Consistent with the solution binding results, karyopherin beta 2 inhibited karyopherin alpha/beta 1-mediated import of a classical NLS containing substrate and, vice versa, beta 1 inhibited beta 2-mediated import of A1 substrate, suggesting that the two import pathways merge at the level of docking of beta 1 and beta 2 to repeat nucleoporins.